L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of Acetyl L Carnitine: Benefits and Side Effects Gene Food Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. Over 90% of your body's energy comes from mitochondria. When they break down, everything else does too. Think: Fatigue that sleep doesn't fix Brain fog and memory issues Slow How Acetyl L Carnitine Works HowStuffWorks Does L Carnitine Help with Erectile Dysfunction?